"He looked really good," Burns said. "His changeup looked pretty nice, I was definitely chasing it. He was spotting up, threw me a nice 3-2 heater right on the inside black, and I barely fought it off. His fastball had really good life and a little bit of run too."

"He's ramping it up each time," A's manager Bob Melvin said. "Really looks like he could be in a game the way he's throwing. He's very excited when he's out there on the mound."

The A's will make sure Alvarez rebounds from the outing with no issues before announcing his next step, though it's presumed to be another simulated game. He could potentially throw two more of those before beginning a Minor League rehab assignment.

"It's already looking like he's throwing pretty hard," Burns said. "Everything had good movement, and it's a little bit hard to pick up the ball out of his hand. He hides it well and has a quick arm action, so it definitely adds to his deceptiveness."

Alvarez, who will turn 26 on Monday, was signed by the A's to a one-year deal this offseason. He was an All-Star with Miami in 2014.